[1] Thomas Jefferson Univ, Sidney Kimmel Med Coll, Dept Emergency Med, 1025 Walnut St,Suite 300, Philadelphia, PA 19017 USA
[2] Beth Israel Deaconess Med Ctr, Ctr Resuscitat Sci, Boston, MA 02215 USA
[3] Univ Penn, Perelman Sch Med, Div Pulm Crit Care Med, Philadelphia, PA 19104 USA
[4] Univ Colorado, Sch Med, Dept Emergency Med, Aurora, CO USA